1. Field of the Invention
The present invention relates generally to retractors for use in heart surgery and, more particularly, to retractors for use during open-heart surgery.
2. Description of the Prior Art
The heart is a hollow muscular pump located in the chest cavity in a loose protective sack called the pericardium. The heart is comprised of a thick muscular layer called the myocardium, which defines four chambers that include two upper chambers, the atria, and two lower chambers, the ventricles. The atrium and ventricle on the right side are separated by a tricuspid valve, while the atrium and ventricle on the left side are separated by a bicuspid (mitral) valve. The right-side atrium and ventricle are separated from the left-side atrium and ventricle by a wall known as the septum.
Normally, the heart beats in a continuous, regular rhythm. Sometimes, however, the heart beats in an irregular rhythm that frequently is caused by atrial fibrillation. Atrial fibrillation is an abnormal heart rhythm that originates in the atria. Instead of electrical impulses traveling in an orderly fashion through the heart, many impulses begin and spread through the atria, causing a rapid and disorganized heartbeat. Research has shown that the majority of undesired electrical activity (foci) come from the areas around the four pulmonary veins. Other less common areas include the superior vena cava, right and left atria, and the coronary sinus. While it once was thought that atrial fibrillation was harmless, it now is known that atrial fibrillation is associated with heart failure, blood clots, a five- to sevenfold increase in stroke, and increased mortality from heart disease.
There are a number of techniques that can be used to correct or alleviate atrial fibrillation. One popular non-surgical technique is pulmonary vein isolation ablation. In this technique, special catheters are inserted through the right atrium and the septum into the left atrium. The catheters are used for mapping locations of abnormal electrical impulses and for delivering energy to the atrium in the region of the atrium that connects to the pulmonary veins. The catheters produce circular scars that block any electrical impulses from firing within the pulmonary veins, thus preventing atrial fibrillation.
Unfortunately, non-surgical procedures such as pulmonary vein isolation ablation are not suitable to correct atrial fibrillation in all cases. Atrial fibrillation is very common, and those with atrial fibrillation often have concurrent heart disease such as coronary artery disease or valve disease that requires surgical treatment. In such cases, it is necessary to expose the heart by conducting open-heart surgery in order to have access to the interior of the heart.
During a typical open-heart surgical procedure, the chest is incised along the sternum. A thoracic retractor separates the split sternum in order to expose the heart. Specifically, the thoracic retractor includes grips that fit on either side of the incision and which can be moved apart to expose the heart. The grips maintain the incision open for the duration of the open-heart surgical procedure. Further, the thoracic retractor provides a platform to which cardiovascular retractors and other surgical equipment can be attached and anchored.
A fairly recent type of open-heart surgical procedure to correct atrial fibrillation is the so-called Maze procedure. The January, 2000 issue of “Seminars in Thoracic and Cardiovascular Surgery” is a compendium of articles about the Maze procedure published by W.B. Saunders Publishing Company, and is hereby incorporated by reference in its entirety. In the Maze procedure as originally practiced, precise incisions were created in the right and left atria. Because scar tissue can block errant electrical impulses, the scar tissue generated by the incisions can block routes of errant electrical impulses responsible for atrial fibrillation. Specifically, the scar tissue can direct normal sinus impulses to travel to the atrioventricular node as they normally should. Recently, the Maze procedure has been altered to focus mainly on the left atrium, because the vast majority of irregular foci come from areas around the four pulmonary veins and those veins are connected to the left atrium.
During the Maze procedure as presently practiced, the incised myocardium is retracted to move portions of the heart tissue and to expose the pulmonary veins and the artial appendage. The retraction can be accomplished manually by an assistant using a hand-held retractor blade that contacts the tissue adjacent to the mitral valve. Unfortunately, manual retraction is quite undesirable for a number of reasons, including the need for the continual presence of an assistant to manipulate the retractor, and the inconsistency and variability of the retraction so provided.
An alternative technique to retract the heart tissue and expose the pulmonary veins and the atrial appendage is to use a plurality of relatively narrow, short retractor blades that are mounted onto the thoracic retractor. The retractor blades are not properly configured to retract the heart tissues to perform the Maze procedure. The previously known retractors blades cooperate with each other to retract and retain the heart tissue in a retracted position for the duration of the procedure. Each of the blades (up to three or more in number) must be individually placed and set by a surgeon to contact the inner heart wall adjacent to the mitral valve and the pulmonary veins so as to retract the heart tissue and expose the pulmonary veins and the atrial appendage. Placing and setting each of the blades takes a certain amount of time. In addition, each of the blades places a localized pressure on the heart tissue. Desirably, a retraction technique would be available that would decrease the time required to perform the surgical procedure as well as to decrease and delocalize the pressure on the heart tissue.